Transport characteristics of ramp-type YBa2Cu3O7-δ/PrBa2Cu3O7-y/YBa2Cu3O7-δ Josephson junctions

The transport behaviors of YBa2Cu3O7-δ/PrBa2Cu3O7-y/YBa2Cu3O7-δ junctions with barrier thickness ranging from 6 to 30 nm were studied. In these junctions, the existence of a proximity layer was confirmed by the appearence of a temperature-dependent coherence length. The structure of the junctions changed from SNS to SNINS with increasing barrier thickness. It was found that the quasiparticles transport through a thin barrier by metallic conduction and through a thick barrier by tunneling conduction. In junctions with a moderate barrier thickness, we found a subgaplike feature in the conductance-voltage curves, which could be related to multiple Andreev reflection in a SNcNS Josephson junction. For junctions with a thick barrier, the dependence of conductance on temperature could be well fitted by the T4/3 law. This suggested that the quasiparticles transport across a thick PrBa2Cu3O7-y barrier layer via two localized states in an inelastic tunneling process.published_or_final_versio

Protopine Inhibits Heterotypic Celladhesion In Mda-Mb-231 Cells Through Down-Regulation Of Multi-Adhesive Factors

Background: A Chinese herb Corydalis yanhusuo W.T. Wang that showed anticancer and anti-angiogenesis effects in our previous studies was presented for further studies. In the present study, we studied the anticancer proliferation and adhesion effects of five alkaloids which were isolated from Corydalis yanhusuo.Materials and Methods: MTT dose response curves, cell migration assay, cell invasion assay, as well as three types of cell adhesive assay were performed on MDA-MB-231 human breast cancer cells. The mechanism of the compounds on inhibiting heterotypic cell adhesion were further explored by determining the expression of epidermal growth factor receptor (EGFR), Intercellular adhesion molecule 1 (ICAM-1), αv-integrin, β1- integrin and β5- integrin by western blotting assay.Results: In five tested alkaloids, only protopine exhibited anti-adhesive and anti-invasion effects in MDA-MB-231 cells, which contributed to the anti-metastasis effect of Corydalis yanhusuo. The results showed that after treatment with protopine for 90 min, the expression of EGFR, ICAM-1, αv-integrin, β1- integrin and β5- integrin were remarkably reduced.Conclusion: The present results suggest that protopine seems to inhibit the heterotypic cell adhesion between MDA-MB-231 cells, and human umbilical vein endothelial cells by changing the expression of adhesive factors.Keywords: Corydalis yanhusuo, Protopine, Adhesion, Breast cancer, Integrin

Interfacial microstructures in ramp type multilayer Josephson junctions studied by TEM

The microstructures of high Tc ramp type Josephson junctions were studied by using transmission electron microscopy. The work was emphasized at the interfacial defects and the influence of the ramp slope. The results show that for the ramp slope angles of 15°~40°, the epitaxy was still remained through all layers at the ramp region without the formation of big grain boundaries. No amorphous layers and secondary phases were observed at the barrier interfaces. For a gentle ramp junction, small misoriented grains appeared in some portions of the barrier. The substrate ramp formed during the ion etching process had little influence on the growth of the upper layers. In junctions with a steep ramp, defects increased near the interface, although the epitaxy of the barrier was of good quality. The results demonstrate that the slope angle of the junction ramp is an important factor that influences the performance of the Josephson junctions.published_or_final_versio

Preparation of continually graded barriers of YPrBaCuO for HTS Josephson junctions

We report preparation of a novel barrier structure for high Tc superconducting multilayer Josephson junctions using a simple composite target technique. Such a barrier consists of Yx Pr1-xBa2Cu3Oy with a continually varied concentration of yttrium. In this barrier no lattice mismatch and other incompatibility problems occur between adjacent layers. Thus the formation of interfacial defects and structural strain can be mostly prevented. The Josephson coupling takes place at the electrically formed interfaces rather than the structural interfaces. A particular feature of these junctions is that the effective thickness of the barrier strongly depends on the measuring temperature and the concentration gradient. The absence of the structural interface in the weak link region greatly enhances the reproducibility and the performance of these junctions.published_or_final_versio

High-Tc ramp-type Josephson junctions with a continually graded Y1–xPrxBa2Cu3Oy barrier

High-Tc Josephson junctions with a graded barrier have been prepared by using a composite target. Such a barrier is synthesized by utilizing Y1–xPrxBa2Cu3Oy with a continually graded concentration of Pr, in which no lattice mismatch and other incompatible problems take place. The structural interfaces are absent in the weak link region and Josephson coupling occurs at the naturally formed superconducting/normal interfaces within the Y1–xPrxBa2Cu3Oy layer. Thus, it can significantly enhance the reproducibilty and performance of these junctions. The temperature dependences of the barrier thickness and Josephson were also studied. © 2001 American Institute of Physics.published_or_final_versio

The effect of normal and abnormal ageing on prospective memory showed increased cognitive conflict: a functional MRI study

INTRODUCTION: Prospective memory (PM) is memory for planned intention, which needs to be executed appropriately in the future. PM task is usually embedded in ongoing activities. The neural correlates of PM have not been elucidated. To date, no functional imaging study has been conducted to examine the relevant functional change of PM during the processes of ageing and ...published_or_final_versio

Relevance of short-range connectivity to brain compensation and cognitive efficiency in healthy and pathological ageing: a combined functional magnetic resonance imaging and tractography study on prospective memory

INTRODUCTION: Cognition and its efficiency are related to the activities of specific brain regions and their interactions. The brain function and structure are vulnerable to both healthy and pathological ageing, and these processes may underlie the impaired cognitive functions in daily life …published_or_final_versio